Pelleted blasting powder



I 14 9-46 l L, Fle'ian Patented Dec. 1, 1936 UNITED STATES hearse time:

PATENT OFFlCE PELLETED BLASTING POWDER No Drawing. Application April 27,1933, Serial No. 668,221

10 Claims.

This invention relates to improved blasting powder compositions and moreparticularly to such deflagrating compositions in the form of blocks orsticks, containing ammonium nitrate as an ingredient.

Black powder has long been known and used as a commercial explosive ofrelatively low velocity. The composition of this explosive has, ingeneral, varied little over a period of many years, a representativecomposition comprising, for example, '72% sodium nitrate, 10% sulfur,and 18% charcoal. While these ingredients have varied somewhat inamounts, the powder has retained, in general, the same approximatecomposition.

Black powder was for many years used in the form of grains of varyingsize. These grains were given a. smooth polished surface coating by theoperation known as glazing.

More recently, however, black blasting powder has been put up and usedin the form of packaged sticks similar to dynamite. These sticks orblocks are produced by several well-known methods.

For example, the so-called pelleted powder has largely replaced thegranular powder recently for blasting Work. Pelleted black blastingpowder is made on a press in the form of cylindrical blocks customarily,about 2 in length and of any desired diameter, for example, up toapproximate1y'2". Ordinarily, these pellets have a hole runninglongitudinally through their centers, this hole being about A," indiameter. It is the practice to wrap together several of these pellets,placed end to end, in a roll of paper to make a packaged explosivesimilar in form to a stick of dynamite.

Another method of producing black blasting powder in stick form is topack the loose powder in a formed cylindrical paper shell. Preferably,the wet powder containing, for example 4% to 8% of water is packedlightly in the shell. The powder is then dried in the shell. When dry,the shells are completely closed and, if desired, protected fromatmospheric moisture by coating with parafiin or similar means. Suchpowders also have a longitudinal center hole, for facilitating ignitionand combustion.

The use of such packaged powder in stick form brings many apparentadvantages, not only in ease of handling and freedom from fire andexplosion hazards, but in increased convenience in the loading of boreholes as well. In actual blasting, the powder may be used in wholepackages or sticks having the length of approximately 8", or in portionsof such sticks.

The object of my invention is to produce a new and improved blastingpowder in stick form, characterized by its high strength, this strengthbeing capable of control by adjustment of the composition of the powder.A further object is a formed block of black blasting powder having arelatively low density. Additional objects will be apparent as theinvention is further described and disclosed hereinafter.

These objects are accomplished by including among other things ammoniumnitrate as an ingredient in my improved powder. In such a composition,the ammonium nitrate replaces with beneficial results a portion of thesodium nitrate or other inorganic nitrates commonly used in suchblasting powder compositions. I find, however, that it is not desirableto replace all the sodium nitrate in the powder by ammonium nitrate,since with such high percentages of ammonium nitrate, the powder tendsto become a detonating rather than a defiagrating explosive.

I find that the replacement of a portion of the sodium nitrate byammonium nitrate in black blasting powder compositions brings about increased explosive strength. This increase in strength is due principallyto the fact that the ammonium nitrate on combustion produces gaseousdecomposition products only, whereas a considerable portion of thedecomposition products of sodium nitrate is made up of solid materials.The increased strength of the ammonium nitrate powders results thereforefrom the increased gas volume from a given weight of powder. Byreplacing greater or smaller portions of the sodium nitrate heretoforeused by ammonium nitrate, the strength of the powder may be effectivelycontrolled. I preferably use between and 30% ammonium nitrate in myimproved powder compositions, since less than 5% does not give thedesired improved properties, while more than 30% ammonium nitraterenders the powder less readily combustible and more subject todetonation.

The pelleted powders produced previously have had a greater strengththan was necessary or desirable in many cases. For this reason, lowdensity powders have a very practical application, since by their use asmaller weight of explosive is required and a better distribution of theexplosive pressure within the bore-hole is possible.

The incorporation of ammonium nitrate in black blasting powders in placeof a portion of the sodium nitrate brings about a lower density in thefinished explosive, due doubtless to the fact that the density ofammonium nitrate itself is lower than that of sodium nitrate,approximately 1.72 against 2.27. I have found, however, that powderscontaining ammonium nitrate may be produced having much lower densitiesthan have been obtained heretofore. I obtain this result preferably bylightly packing the wet powder, having a water content between 4 and 8%for example, in a container which will preserve the form of the packedexplosive and in which it is dried and permitted to set into a hardblock. The removal of the water from the powder brings about arelatively low density, which may be controlled by varying the pressureexerted in packing the powder into the shells.

While low density black blasting powder containing ammonium nitrate maybe obtained in stick form, as described heretofore, I find that theselow densities may readily be obtained by the introduction of low densitycarbonaceous materials. While many different ingredients of this naturemay be used, such as wood pulp, low density ingredients such as variousvegetable piths, bagasse pith, cornstalk pith, and the like, Ipreferably use wood pulp because of its ready availability and itssatisfactory properties for such use. Fibrous carbonaceous material hasthe advantage of imparting cohesiveness as well as low densityproperties to the block of blasting powder.

I am aware that ammonium nitrate has been used as an ingredient ofdeflagrating blasting powders in the prior art. The use of ammoniumnitrate, however, has particular advantage in the case of low densityblasting powders. When incorporated into the formulas of high densitypowders, ammonium nitrate retards the rate of combustion of the powdertoo greatly. I have found, however, that ammonium nitrate does not havethis retarding effect in the low density powders according to myinvention. At the same time, the use of ammonium nitrate makes possiblethe maintenance of the bulk strength of the powder, even with greatlydecreased densities and increased stick counts.

My invention therefore makes possible a new type of black blastingpowder with desirable properties such as have been unattainablepreviously, namely the combination of high strength, low density, andsatisfactory velocity of combustion.

By way of illustration of my invention by specific embodiments, thefollowing examples are given of powder compositions showing thedesirable properties imparted by the incorporation of ammonium nitrateas an ingredient of black blasting powders in low density stick form.

the shells with one end of the shell open. When dry, the shells wereclosed and given a waterproof coating.

The summary table following, based on the foregoing tabulation, veryclearly shows the effects of increasing ammonium nitrate contents and ofdecreasing densities with powders containing 10% ammonium nitrate, forexample. It is seen that, as the density of the powder decreases, therate of pressure development increases with the strength remainingsubstantially constant for a given volume of powder, in spite of thelower weight. The same tendency is indicated with powders having the 20%content of ammonium nitrate. It will be seen, also, from the tabulationthat an increase in the amount of ammonium nitrate present for a givendensity results in an increased rate of burning contrary to what wouldhave been expected from experience with high density powders.

Bulk strength I f t Velifwityrate Ammonium 1. o. o cgs. 0 press.

nitrate Denslty per 50 lbs. Max. pres- (level. per

sure per clg.

ctg.

The examples cited in the tables heretofore have all been powders madefrom wheel cake, in order that the values obtained might be comparable.It should be understood, however, that my invention is intended to coveralso blocks of powder made of grained powder, in which case higher ratesof pressure development will be obtained.

By the use of ammonium nitrate as an ingredient, together with a fibrouscarbonaceous material, it is possible to obtain powders of densitieslower than 1.30 and weighing less than 175 grams for a 1%" x8 cartridge,corresponding to not less than approximately 130 such cartridges to a50-pound case. The lowest density shown in the table for such a powderis 1.01, and densities as low as 0.90 are attainable.

The strength values given in the tabulation are those obtained when a1%" x 8 cartridge of the powder is shot in a closed bomb of 20-litersvolume, for example in the Bichel bomb. The values for the rate ofpressure development were obtained also by the use of the sameapparatus.

Compositions 1 2 3 4 5 6 7 8 Ammonium nitrate 0. 0 0. 0 10. 0 10. 0 10.020.0 20. 0 20. 0 Sodium nitrate- 72. 0 70. 5 60. 5 60. 5 60.5 50. 5 50.5 50. 5 Charcoal 18. 0 l5. 6 l5. 6 15. 6 15. 6 15.6 15.6 15. 6 Sul 10. 08. 6 8. 0 8. 6 8. 6 8. 0 8. 6 8. 0 Calcium carbonate--- 0. 0 1. 3 1.3 1. 3 1. 3 1. 3 1. 3 1.3 Wood pulp 0.0 4.0 4. 0 4.0 4.0 4. 0 4. 0 4, 0Apparent density 1. 30 1.18 1. 25 l. 22 1. 15 1. 25 1. 2 1.01 Rate ofpress. dev. kg./sq. cm./sec./c 129 110 110 125 235 130 220 230Strength-Pressure (lev. kgJsq. cm./ctg (1% 30. 7 29. 2 29.9 28. 9 30.834. 5 33. 4 31. 4 Wt. ctg.-gms.l}4" x 8 178 163 168 164 156 168 153Otg./50 lb. case 128 139 135 138 135 148 102 In the foregoing table, thepowders shown were prepared by punching into 1 x 8" formed paper shellswet compositions of Wheel cake powder having a moisture content between6 and 7%. At this moisture content, the powder was soft and cohesive.The powders were then dried in It will be understood that manyvariations from the compositions cited may be made without departingfrom the spirit of the invention. The sodium nitrate, for example, maybe replaced, if desired, by potassium nitrate, calcium nitrate, or othersuitable inorganic nitrate. Ad-

ditions of suitable acid-accepting materials such as calcium carbonatemay be made also, along with wood pulp or other fibrous carbonaceousmaterial. I intend to be limited in my invention only as indicated bythe following patent claims.

I claim:

1. A formed block of deflagrating blasting powder, characterized by itshigh strength and having a density less than 1.30, said block comprisinga modified black powder composition containing ammonium nitrate as aningredient.

2. A formed block of deflagrating blasting powder, characterized by itshigh strength and having a density between about 0.90 and less than1.30, said block comprising a modified black powder compositioncontaining ammonium nitrate as an ingredient.

3. A formed block of deflagrating blasting powder characterized by itshigh strength and having a density less than 1.30, said block comprisinga modified black powder composition containing 5 to 30% ammoniumnitrate.

4. A formed block of deflagrating blasting powder, characterized by itshigh strength and having a density between about 0.90 and less than1.30, said block comprising a modified black powder compositioncontaining 40 to sodium nitrate, 1 to 20% charcoal, 1 to 20% sulfur, and5 to 30% ammonium nitrate.

5. A formed block of deflagrating blasting powder, characterized by itshigh strength and low density of less than 1.30, comprising a modifiedblack powder composition containing as ingredients ammonium nitrate anda low density carbonaceous material.

6. A formed block of deflagrating blasting powder, characterized by itshigh strength and low density of less than 1.30, comprising a modified.black powder composition containing as ingredients ammonium nitrate andwood pulp.

7. A formed block of deflagrating blasting powder, characterized by itshigh strength and low density of less than 1.30, comprising a modifiedblack powder composition containing 5 to 30% of ammonium nitrate and alow density carbonaceous combustible material.

8. A formed block of deflagrating blasting powder, characterized by itshigh strength and having a density between about 0.90 and less than1.30, said block comprising a modified black powder compositioncontaining as ingredients ammonium nitrate and wood pulp.

9. A formed block of deflagrating blasting powder, characterized by itshigh strength and having a density less than 1.30, said block comprisinga modified black powder composition containing 5 to 30% ammonium nitrateand 1 to 10% of a low density carbonaceous combustible material.

10. A formed block of defiagrating blasting powder characterized by itshigh strength and having a density between about 0.9 and less than 1.30,said block comprising a modified black powder composition containing 5to 30% ammonium nitrate, 40 to 75% sodium nitrate, 1 to 20% charcoal, 1to 20% sulfur, and 1 to 10% Wood pulp.

WILLIAM E. KIRST.

